An internal combustion engine of a vehicle may be automatically stopped during conditions when a driver is requesting less than a threshold amount of torque. The engine may be automatically stopped while the vehicle is decelerating or after the vehicle has come to a complete stop. During automatic engine stop, delivery of fuel to the engine may cease and engine rotation may stop. By ceasing combustion and stopping the engine, it may be possible to conserve fuel and extend driving range of a vehicle. It may be desirable to stop the engine frequently to increase vehicle fuel economy. However, if the vehicle's battery is in a low state of charge, the engine may not restart due to insufficient engine cranking torque. Further, if the engine is stopped, it may take longer than a threshold amount of time to restart the engine. The engine starting time may increase when there is partial degradation of the engine cranking system. For example, the engine cranking time may increase when battery state of charge is low, battery internal resistance is high, aged starter, or when engine lubrication is different than is expected. The engine cranking time may be within an expected threshold time duration when components of the engine cranking system are not degraded. A driver or passenger of the vehicle may notice an extended engine cranking time and find it to be objectionable.
The inventor herein has recognized the above-mentioned issues and have developed a vehicle operating method, comprising: automatically stopping and starting an engine; and prohibiting automatic stopping of the engine in response to an estimated engine cranking time exceeding a threshold.
By prohibiting or not permitting automatic engine stopping in response to an estimated engine cranking time, it may be possible to prevent excessive engine cranking times while still permitting automatic engine stopping when engine cranking times are expected to be short. Consequently, at least a portion of vehicle fuel economy gains achieved through automatic engine stopping may be preserved without vehicle occupants having to endure long engine cranking times. Further, estimates of engine cranking durations may be revised to reflect data captured during most recent automatic engine starting conditions so that the engine cranking estimates may be made more accurate.
The present description may provide several advantages. For example, the approach may reduce the possibility of vehicle occupants objecting to long engine cranking times. Further, the approach enables fuel to be conserved by permitting automatic engine stopping and starting when engine cranking times are expected or estimated to be less than a threshold amount of time. In addition, the approach may dynamically change how engine cranking time is estimated to accommodate different vehicle platforms and to maintain system functionality during some conditions of system degradation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.